State officials will hold two public meetings Tuesday to update Minneapolis residents living near a former General Mills Superfund Site about a potential vapor problem in their neighborhood.

Recent soil tests in a small section of the Como neighborhood show that vapor levels from a common solvent exceed government health limits for indoor air. State officials say they need to test about 200 homes in the area to make sure that the vapors aren't seeping into residents' basements.

General Mills used trichloroethylene at its Como neighborhood research site in Minneapolis from the 1940s to the early 1960s. Research staff probably used the solvent as a cleaner or degreaser, a company spokesman said. When they were done with the chemical, also known as TCE, employees dumped it into large drums that were buried about 10 to 12 feet deep in a pit on the company's property.

General Mills disposed of about 1,000 gallons of TCE in the pit each year for 15 years, said Hans Neve, a supervisor with the Minnesota Pollution Control Agency's Superfund program.

"The state of understanding was if you put waste solvents into a pit they go away; they go to this place called 'away,'" Neve said. "As knowledge and understanding about contaminants developed we learned that there isn't a place called 'away.' There is no such place. That practice is almost certainly going to cause groundwater contamination and that's what happened."

When the solvents were discovered in the groundwater in the early 1980s, the area was listed as a Superfund site and General Mills was ordered to clean it up. The company excavated the pit and installed a pump at the site that filtered the water for 25 years. The groundwater was never used as a drinking water source.

General Mills was in the process of wrapping up its mitigation work at the site when vapor tests conducted this year revealed that some of the soil in the surrounding neighborhood contained an underground vapor cloud, Neve said.

Vapor mapCourtesy MPCA

Officials don't know if the underground contamination is getting into homes "and that's what we need to understand to bring this towards resolution," said Neve.

If vapors are getting into homes, it could make residents sick.

"It is toxic when it's breathed, as well as when it's ingested," said Rita Messing, a research scientist supervisor at the Minnesota Department of Health. "So it is problematical."

Long-term exposure to TCE has been associated with liver, kidney and blood cancers. But health officials say they are more concerned about some of the short-term effects of inhaling vapors from the solvent. Messing says at high levels of exposure the chemical can cause immune system problems that make a person more susceptible to infections. It also has been associated with fetal heart abnormalities.

The health department has already scanned its birth defects registry and Messing says there is no evidence of a problem in the Como neighborhood. But while the registry data is reassuring, Messing says it's not a substitution for testing homes.

"The problem is right now we don't have any data," she said. "So I want to make that clear that we really don't know what we're going to see until we actually measure."

The Minnesota Pollution Control Agency has asked everyone in a several-block area near the waste site to allow officials to sample the air underneath their basements. They'll explain the process to residents during two public meetings Tuesday.

General Mills will pay for the testing, and the installation of a ventilation system in any home where elevated TCE vapor levels are found.

Spokesman Tom Forsythe says the company is cooperating fully with the state's investigation.

"This is our home," Forsythe said. "We've been here a very long time. And we're going to make this right. So if there is an issue we're going to address it."

Forsythe says General Mills has lined up numerous contractors to perform the testing and any vapor mitigation knowing that residents will want to know quickly if there is a problem with the air in their homes. He says the company has the capacity to do 50 tests a week, starting as soon as next week.